Logger.h

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// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
 
#ifndef WPIUTIL_WPI_LOGGER_H_
#define WPIUTIL_WPI_LOGGER_H_
 
#include <functional>
#include <utility>
 
#include <fmt/format.h>
 
namespace wpi {
 
enum LogLevel {
  WPI_LOG_CRITICAL = 50,
  WPI_LOG_ERROR = 40,
  WPI_LOG_WARNING = 30,
  WPI_LOG_INFO = 20,
  WPI_LOG_DEBUG = 10,
  WPI_LOG_DEBUG1 = 9,
  WPI_LOG_DEBUG2 = 8,
  WPI_LOG_DEBUG3 = 7,
  WPI_LOG_DEBUG4 = 6
};
 
class Logger {
 public:
  using LogFunc = std::function<void(unsigned int level, const char* file,
                                     unsigned int line, const char* msg)>;
 
  Logger() = default;
  explicit Logger(LogFunc func) : m_func(std::move(func)) {}
  Logger(LogFunc func, unsigned int min_level)
      : m_func(std::move(func)), m_min_level(min_level) {}
 
  void SetLogger(LogFunc func) { m_func = func; }
 
  void set_min_level(unsigned int level) { m_min_level = level; }
  unsigned int min_level() const { return m_min_level; }
 
  void DoLog(unsigned int level, const char* file, unsigned int line,
             const char* msg);
 
  void LogV(unsigned int level, const char* file, unsigned int line,
            fmt::string_view format, fmt::format_args args);
 
  template <typename... Args>
  void Log(unsigned int level, const char* file, unsigned int line,
           fmt::string_view format, Args&&... args) {
    if (m_func && level >= m_min_level) {
      LogV(level, file, line, format, fmt::make_format_args(args...));
    }
  }
 
  bool HasLogger() const { return m_func != nullptr; }
 
 private:
  LogFunc m_func;
  unsigned int m_min_level = 20;
};
 
// C++20 relaxed the number of arguments to variadics, but Apple Clang's
// warnings haven't caught up yet: https://stackoverflow.com/a/67996331
#ifdef __clang__
#pragma clang diagnostic ignored "-Wgnu-zero-variadic-macro-arguments"
#endif
 
#define WPI_LOG(logger_inst, level, format, ...)                         \
  if ((logger_inst).HasLogger() && level >= (logger_inst).min_level()) { \
    (logger_inst)                                                        \
        .Log(level, __FILE__, __LINE__,                                  \
             FMT_STRING(format) __VA_OPT__(, ) __VA_ARGS__);             \
  }
 
#define WPI_ERROR(inst, format, ...) \
  WPI_LOG(inst, ::wpi::WPI_LOG_ERROR, format __VA_OPT__(, ) __VA_ARGS__)
#define WPI_WARNING(inst, format, ...) \
  WPI_LOG(inst, ::wpi::WPI_LOG_WARNING, format __VA_OPT__(, ) __VA_ARGS__)
#define WPI_INFO(inst, format, ...) \
  WPI_LOG(inst, ::wpi::WPI_LOG_INFO, format __VA_OPT__(, ) __VA_ARGS__)
#define WPI_DEBUG(inst, format, ...) \
  WPI_LOG(inst, ::wpi::WPI_LOG_DEBUG, format __VA_OPT__(, ) __VA_ARGS__)
#define WPI_DEBUG1(inst, format, ...) \
  WPI_LOG(inst, ::wpi::WPI_LOG_DEBUG1, format __VA_OPT__(, ) __VA_ARGS__)
#define WPI_DEBUG2(inst, format, ...) \
  WPI_LOG(inst, ::wpi::WPI_LOG_DEBUG2, format __VA_OPT__(, ) __VA_ARGS__)
#define WPI_DEBUG3(inst, format, ...) \
  WPI_LOG(inst, ::wpi::WPI_LOG_DEBUG3, format __VA_OPT__(, ) __VA_ARGS__)
#define WPI_DEBUG4(inst, format, ...) \
  WPI_LOG(inst, ::wpi::WPI_LOG_DEBUG4, format __VA_OPT__(, ) __VA_ARGS__)
 
}  // namespace wpi
 
#endif  // WPIUTIL_WPI_LOGGER_H_